What Makes Us Fat: Is It Eating Too Much Or Moving Too Little?

We're constantly hearing messages that we're eating too much and not moving around enough. Now researchers suggest that we're actually not eating more than we did 20 years ago, it's that we're much less active. And that includes not just middle-aged workers tied to their desks, but also young men and women who spend their days sitting in front of their laptops.

To try to figure out the impact of food versus activity, Dr. Uri Ladabaum, a professor of medicine at the Stanford University School of Medicine, looked at federally collected health data from the NHANES program from 1988 and compared it to 2010.

He expected to find people eating more over the past two decades. But instead, he found that caloric intake remained about the same, "which may seem a little surprising given the trends in portion size and the popular belief that we're eating more and more," he said.

"It may well be that we're eating too much, but it doesn't seem that we are accelerating our caloric intake," Ladabaum added.

For example, it could well be that we were already eating too much back in 1988, compared with earlier decades. Even so, Ladabaum found the biggest changes were in the amount of physical activity.

Back in the 1980s, 80 to 90 percent of people reported doing at least some physical activity in their leisure time. But now, up to half of Americans say they are not active at all.

And that's likely an underestimate, Ladabaum says, because people tend to overestimate their activity.

All age groups became less active, but one of the biggest surprises was in men and women between the ages of 18 and 39. The number of white and African-American women getting no activity more than tripled; that number almost doubled for Mexican-American women.

For white and African-American men, the people who were inactive more than tripled. And among Mexican-American men, rates doubled.

This doesn't mean food is not to blame, Ladabaum says.

"This is something some of my colleagues have framed as 'Is it gluttony or is it sloth?' Those are not nice words, but those are the terms in which some people think about this debate," says Ladabaum. "So anybody looking for a simple explanation, either A or B, we're not going to find that; it's clearly both."

The problem of inactivity is exacerbated by a changing job market that's taken Americans from the physically demanding manufacturing floor to sitting behind a desk.

"In 1960, 1 out of 2 Americans had a job where they had lots of physical activity and actually exercised at work; by 2008, very few Americans do work that doesn't involve sitting around all day," according to Dr. Tim Church, a professor of preventative medicine at the Pennington Biomedical Research Center at Louisiana State University.

His research found that only 1 in 5 Americans move on the job, but Church says that's likely a "gross underestimate," adding that it's probably more like 1 in 10.

"We have these great old pictures seeing cars being built in the '60s, and these men were physically picking up a bumper and putting it onto a car," Church says. "Then you get pictures of cars being built now, and there's not even a human being in the room. These computers grab bumpers, put them on the car, and they are then bolted on by another big electronic arm."

Church took the findings one step further and calculated how many calories were no longer being burned. He found it was about 140 fewer calories burned a day for men and 120 fewer calories burned a day for women. "That doesn't sound like much, but when it's day after day after day, it adds up," he says.

So what's a modern cube rat to do? Church says given that the workplace has become so sedentary, it's critical for people to be more active off the job.

And there are concrete steps people can take to change our sedentary lifestyle. Do as federal guidelines recommend: 30 minutes of moderate exercise such as walking, biking or swimming, at least 5 days a week.

"If you think about 140 calories a day, that's 30 minutes of walking or so, not even a fast pace," Church says.

And that may be all you would need to get that calories in-calories out equation back in balance.

Copyright 2014 NPR. To see more, visit http://www.npr.org/.

Transcript

LINDA WERTHEIMER, HOST:

This is MORNING EDITION from NPR News. I'm Linda Wertheimer.

STEVE INSKEEP, HOST:

And I'm Steve Inskeep. Today in Your Health, preventing weight gain. The usual suspects in America's obesity epidemic are eating too much and not getting enough exercise. Now a new study suggests that Americans actually are not eating more than we did 20 years ago. It's the amount of physical activity that's changed. NPR's Patti Neighmond reports.

PATTI NEIGHMOND, BYLINE: Dr. Uri Ladabaum wanted to understand more about the reasons for the obesity epidemic. He decided to dig through 20 years' worth of health information. Ladabaum's a gastroenterologist at Stanford University. He looked at government surveys that asked people how much they ate and how active they were. He compared what people said in 1988 to what they said in 2010.

URI LADABAUM: In the early time periods, approximately 10 to 20 percent of people reported no leisure time physical activity, meaning that 80 to 90 percent reported doing at least some physical activity in their leisure time, whereas in more recent time periods, it was up to half who said they weren't doing any leisure time physical activity.

NEIGHMOND: And he says that's likely an underestimate because people tend to overestimate how active they are. When it came to food, Ladabaum expected to find people eating more over the past two decades. Instead, he found the daily calorie counts stayed about the same.

LADABAUM: Which may seem a little surprising given the trends in portion size and so on and the popular belief that we're eating more and more. So it may well be that we're eating too much, but it doesn't seem that we are accelerating our caloric intake.

NEIGHMOND: Ladabaum says it's difficult to figure out how much of the epidemic comes from eating too much and how much from not getting enough exercise.

LADABAUM: This is something that some of my colleagues have framed as, is it gluttony or sloth? Those are not nice words, but those are the terms in which some people think about this debate. And I think it's clear that there are contributions to this both from the energy-intake side, how much we're eating, and the energy-expenditure side. So anyone looking for a simple explanation, it's either A or B; we're not going to find that. It's clearly both.

NEIGHMOND: And when it comes to activity, our lives have literally done a 180, not only during leisure time but also on the job. Dr. Tim Church is an obesity specialist at the Pennington Biomedical Research Center

TIM CHURCH: In 1960, 1 of 2 Americans had a job which required a lot of physical activity. They essentially exercised at work. By the year 2008, very few Americans - actually we, you know, do work that doesn't involve sitting around all day.

NEIGHMOND: Church recently looked at federal job surveys over 40 years.

CHURCH: And we have these great old pictures of these cars being built in the '60s, and these men were physically picking up a bumper and putting it onto the car. And then you get these pictures of these cars being built, you know. Now there's not even a human being in the room. There's these computers that grab the bumpers and put it onto the car, and then it's bolted on by another big, electronic arm.

NEIGHMOND: Church wondered how today's lack of movement translates into fewer calories burned and more weight gained. He compared food and activity levels in the 1960s to today and calculated that men now burn 140 fewer calories a day and women 120.

CHURCH: That doesn't sound like much, but when it's day after day after day after day, it adds up.

NEIGHMOND: And often means weight gain over months and years. But Church says there are simple ways to combat this. It takes commitment, and - you probably know what it is - moderate exercise for 30 minutes at least five days a week. Patti Neighmond, NPR News. Transcript provided by NPR, Copyright NPR.